The impact of burning fossil fuels on the environment has been a well-documented problem and has garnered the attention of the international community. One of the major environmental problems confronting many of the countries of the world is atmospheric pollution caused by the emission of pollutants in the exhaust gases and gasoline vapor emissions from gasoline fueled automobiles. This problem is especially acute in major metropolitan areas where atmospheric conditions and the great number of automobiles result in aggravated conditions. While vehicle emissions have been reduced substantially, air quality still needs improvement. The result has been that regulations have been passed to further reduce such emissions by controlling the composition of fuels for automobiles and other motor vehicles. These specially formulated, low emission fuels are often referred to as reformulated or blended fuels and include, for example, various blended gasolines.
Governments and regulatory authorities throughout the world have focused on setting specifications for low emission blended gasoline. The specifications, however, require the presence of oxygenates in the gasoline. Oxygenated gasoline is a mixture of conventional hydrocarbon-based gasoline and one or more oxygenates. The current oxygenates used in blended gasolines belong to one of two classes of organic molecules: alcohols and ethers. More specifically, the primary oxygen-containing compounds employed in blended fuels today are methyl tertiary butyl ether (MTBE) and ethanol. While MTBE achieves its intended purpose of oxygenating the gasoline, the presence of ethers has begun to raise environmental concerns, such as contaminated ground and drinking water. Accordingly, more attention has recently been focused on ethanol oxygenated gasolines.
Ethanol fuel mixtures are a mixture of ethanol and gasoline and are designated with “E” numbers which describe the percentage of ethanol in the mixture by volume. A wide range of ethanol fuel mixtures are used throughout the world. For example, in the United States, E10 is most commonly used at gas stations. In this regard, E10 can be used in most conventional internal combustion engines without modification or redesign due to the usage of blended fuels. With the introduction of hybrid and other specially modified engines, higher percentages of ethanol have also been made available at selected gas stations. For example, E85 is also being sold at a number of locations throughout the United States. Other parts of the world also use ethanol blended fuels in varying percentages. For example, Brazil primarily uses E25 and many countries of Europe offer E5.
While the environmental benefits of ethanol blended fuels have been documented and the commercial usage has dramatically increased over the years, there remain practical challenges with these alternative fuels. In this regard, one problem with ethanol blended fuels is phase separation. Phase separation occurs when water is present to a minor, but nonetheless significant degree in the fuel. Such water may be introduced into the fuel by condensation of humid air in, for example, the ullage space of the storage tank, seepage of ground water into the storage tank, or possibly through other routes. Ethanol is hydrophilic and therefore has a high affinity for water such that when gasoline containing even small amounts of ethanol comes into contact with a sufficient amount of water (e.g., defined by a saturation point), the water will combine with the ethanol and come out of solution with the gasoline.
Although the ethanol will always combine with water, the ethanol and water will not come out of solution with the gasoline until the saturation point is reached. In any event, when phase separation occurs, stratification of the fuel within the storage tank takes place. In this regard, the water/ethanol mixture generally has a higher density as compared to the remaining gasoline and consequently, upon phase separation, the storage tank includes a lower layer of ethanol and water and an upper layer of gasoline (minus at least a portion of the ethanol of the original blend). The lower the ethanol content of the fuel, the more prone the fuel is to separation, as it takes a smaller amount of water to reach the saturation point of the blended fuel.
In a typical fuel dispensing system, such as gas stations and the like, the inlet to the submersible pump which supplies fuel to a dispensing unit is generally located near the lowermost portion of the storage tank. Thus, when phase separation of the blended fuel occurs, the inlet is typically located in the lower ethanol and water layer and the “fuel” that is supplied through the dispensing unit is not the desired blended fuel mixture. Accordingly, engines to which the dispensed fuel is being supplied may not operate properly.
When the blended fuel in the storage tank has separated, the gas station owner has few options for remedying the problem. In this regard, the conventional solution is to evacuate the storage tank and refill the tank with fresh blended fuel. This solution, however, is extremely costly. For example, the dispensing units that access fuel from the separated tank must be shut down so that customers are not able to dispense potentially defective fuel from those units. These shutdowns result in decreased sales and increased consumer dissatisfaction. Additionally, the phase separated fuel is considered a hazardous waste by the EPA and other authorities and must be removed from the tank and transported back to a refinery for reprocessing. Such a process is not only costly, but is time consuming as well.
Various devices have been developed to indicate when phase separation of a blended fuel in the storage tank has occurred. These devices, however, are typically binary type output devices in that they only indicate phase separation or no phase separation (either the fuel is separated or it is not). So long as such a device does not indicate that the fuel has separated, fuel may be supplied to the dispensing units for use by the consumer. Of course once the device indicates that phase separation of the fuel in the storage tank has occurred, the appropriate pumps and dispensing units may be disabled so that the potentially defective fuel is not dispensed to a customer.
While generally being effective for indicating whether phase separation has or has not occurred, such devices do not provide any predictive capabilities, i.e., indicating a risk of phase separation before phase separation actually occurs. In other words, a device that simply indicates whether phase separation has or has not occurred provides minimal value to gas station owners. In this regard, once phase separation of the blended fuel has occurred, it is too late for the gas station owner to take steps that might mitigate or prevent the impending separation, or allow the owner to minimize any potential financial losses caused by the fuel separating into its various phases. As far as the gas station owner is concerned, the only action left to be taken is to remove the separated fuel from the storage tank and refill the tank with fresh blended fuel. Thus, the aforementioned devices do not help the owner mitigate or avoid the high costs associated with the removal and replenishment of fuel when phase separation occurs.
Consequently, there is a need for an improved device and associate methods that can assess, predict or otherwise provide an indication as to the risk of phase separation of a blended fuel in a storage tank prior to the fuel actually separating.